# -*- coding: utf-8 -*-
# Copyright (c) 2012 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

"""Run lint checks on the specified files."""

from __future__ import print_function

import functools
import json
import multiprocessing
import os
import re
import sys

from six.moves import urllib

from chromite.lib import constants
from chromite.cli import command
from chromite.lib import cros_build_lib
from chromite.lib import cros_logging as logging
from chromite.lib import git
from chromite.lib import osutils
from chromite.lib import parallel


# Extract a script's shebang.
SHEBANG_RE = re.compile(r'^#!\s*([^\s]+)(\s+([^\s]+))?')


def _GetProjectPath(path):
  """Find the absolute path of the git checkout that contains |path|."""
  if git.FindRepoCheckoutRoot(path):
    manifest = git.ManifestCheckout.Cached(path)
    return manifest.FindCheckoutFromPath(path).GetPath(absolute=True)
  else:
    # Maybe they're running on a file outside of a checkout.
    # e.g. cros lint ~/foo.py /tmp/test.py
    return os.path.dirname(path)


def _GetPylintrc(path):
  """Locate the pylintrc file that applies to |path|."""
  path = os.path.realpath(path)
  project_path = _GetProjectPath(path)
  parent = os.path.dirname(path)
  while project_path and parent.startswith(project_path):
    pylintrc = os.path.join(parent, 'pylintrc')
    if os.path.isfile(pylintrc):
      break
    parent = os.path.dirname(parent)

  if project_path is None or not os.path.isfile(pylintrc):
    pylintrc = os.path.join(constants.SOURCE_ROOT, 'chromite', 'pylintrc')

  return pylintrc


def _GetPylintGroups(paths):
  """Return a dictionary mapping pylintrc files to lists of paths."""
  groups = {}
  for path in paths:
    pylintrc = _GetPylintrc(path)
    if pylintrc:
      groups.setdefault(pylintrc, []).append(path)
  return groups


def _GetPythonPath(paths):
  """Return the set of Python library paths to use."""
  # Carry through custom PYTHONPATH that the host env has set.
  return os.environ.get('PYTHONPATH', '').split(os.pathsep) + [
      # Add the Portage installation inside the chroot to the Python path.
      # This ensures that scripts that need to import portage can do so.
      os.path.join(constants.SOURCE_ROOT, 'chroot', 'usr', 'lib', 'portage',
                   'pym'),

      # Allow platform projects to be imported by name (e.g. crostestutils).
      os.path.join(constants.SOURCE_ROOT, 'src', 'platform'),

      # Ideally we'd modify meta_path in pylint to handle our virtual chromite
      # module, but that's not possible currently.  We'll have to deal with
      # that at some point if we want `cros lint` to work when the dir is not
      # named 'chromite'.
      constants.SOURCE_ROOT,

      # Also allow scripts to import from their current directory.
  ] + list(set(os.path.dirname(x) for x in paths))


# The mapping between the "cros lint" --output-format flag and cpplint.py
# --output flag.
CPPLINT_OUTPUT_FORMAT_MAP = {
    'colorized': 'emacs',
    'msvs': 'vs7',
    'parseable': 'emacs',
}


# The mapping between the "cros lint" --output-format flag and shellcheck
# flags.
# Note that the msvs mapping here isn't quite VS format, but it's closer than
# the default output.
SHLINT_OUTPUT_FORMAT_MAP = {
    'colorized': ['--color=always'],
    'msvs': ['--format=gcc'],
    'parseable': ['--format=gcc'],
}


def _LinterRunCommand(cmd, debug, **kwargs):
  """Run the linter with common run args set as higher levels expect."""
  return cros_build_lib.run(cmd, error_code_ok=True, print_cmd=debug,
                            debug_level=logging.NOTICE, **kwargs)


def _WhiteSpaceLintData(path, data):
  """Run basic whitespace checks on |data|.

  Args:
    path: The name of the file (for diagnostics).
    data: The file content to lint.

  Returns:
    True if everything passed.
  """
  ret = True

  # Make sure files all have a trailing newline.
  if not data.endswith('\n'):
    ret = False
    logging.warn('%s: file needs a trailing newline', path)

  # Disallow leading & trailing blank lines.
  if data.startswith('\n'):
    ret = False
    logging.warn('%s: delete leading blank lines', path)
  if data.endswith('\n\n'):
    ret = False
    logging.warn('%s: delete trailing blank lines', path)

  for i, line in enumerate(data.splitlines(), start=1):
    if line.rstrip() != line:
      ret = False
      logging.warn('%s:%i: trim trailing whitespace: %s', path, i, line)

  return ret


def _CpplintFile(path, output_format, debug):
  """Returns result of running cpplint on |path|."""
  cmd = [os.path.join(constants.DEPOT_TOOLS_DIR, 'cpplint.py')]
  if output_format != 'default':
    cmd.append('--output=%s' % CPPLINT_OUTPUT_FORMAT_MAP[output_format])
  cmd.append(path)
  return _LinterRunCommand(cmd, debug)


def _PylintFile(path, output_format, debug):
  """Returns result of running pylint on |path|."""
  pylint = os.path.join(constants.DEPOT_TOOLS_DIR, 'pylint-1.7')
  pylintrc = _GetPylintrc(path)
  cmd = [pylint, '--rcfile=%s' % pylintrc]
  if output_format != 'default':
    cmd.append('--output-format=%s' % output_format)
  cmd.append(path)
  extra_env = {
      # TODO(crbug.com/984182): Drop EPYTHON setting if they ever finish.
      'EPYTHON': 'python2',
      'PYTHONPATH': ':'.join(_GetPythonPath([path])),
  }
  return _LinterRunCommand(cmd, debug, extra_env=extra_env)


def _GolintFile(path, _, debug):
  """Returns result of running golint on |path|."""
  # Try using golint if it exists.
  try:
    cmd = ['golint', '-set_exit_status', path]
    return _LinterRunCommand(cmd, debug)
  except cros_build_lib.RunCommandError:
    logging.notice('Install golint for additional go linting.')
    return cros_build_lib.CommandResult('gofmt "%s"' % path,
                                        returncode=0)


def _JsonLintFile(path, _output_format, _debug):
  """Returns result of running json lint checks on |path|."""
  result = cros_build_lib.CommandResult('python -mjson.tool "%s"' % path,
                                        returncode=0)

  data = osutils.ReadFile(path)

  # Strip off leading UTF-8 BOM if it exists.
  if data.startswith(b'\xef\xbb\xbf'):
    data = data[3:]

  # Strip out comments for JSON parsing.
  stripped_data = re.sub(r'^\s*#.*', '', data, flags=re.M)

  # See if it validates.
  try:
    json.loads(stripped_data)
  except ValueError as e:
    result.returncode = 1
    logging.notice('%s: %s', path, e)

  # Check whitespace.
  if not _WhiteSpaceLintData(path, data):
    result.returncode = 1

  return result


def _MarkdownLintFile(path, _output_format, _debug):
  """Returns result of running lint checks on |path|."""
  result = cros_build_lib.CommandResult('mdlint(internal) "%s"' % path,
                                        returncode=0)

  data = osutils.ReadFile(path)

  # Check whitespace.
  if not _WhiteSpaceLintData(path, data):
    result.returncode = 1

  return result


def _ShellLintFile(path, output_format, debug, gentoo_format=False):
  """Returns result of running lint checks on |path|.

  Args:
    path: The path to the script on which to run the linter.
    output_format: The format of the output that the linter should emit. See
                   |SHLINT_OUTPUT_FORMAT_MAP|.
    debug: Whether to print out the linter command.
    gentoo_format: Whether to treat this file as an ebuild style script.

  Returns:
    A CommandResult object.
  """
  # TODO: Try using `checkbashisms`.
  syntax_check = _LinterRunCommand(['bash', '-n', path], debug)
  if syntax_check.returncode != 0:
    return syntax_check

  # Try using shellcheck if it exists.
  shellcheck = osutils.Which('shellcheck')
  if not shellcheck:
    logging.notice('Install shellcheck for additional shell linting.')
    return syntax_check

  # Instruct shellcheck to run itself from the shell script's dir. Note that
  # 'SCRIPTDIR' is a special string that shellcheck rewrites to the dirname of
  # the given path.
  extra_checks = [
      'avoid-nullary-conditions',     # SC2244
      'check-unassigned-uppercase',   # Include uppercase in SC2154
      'require-variable-braces',      # SC2250
  ]
  if not gentoo_format:
    extra_checks.append('quote-safe-variables')  # SC2248

  cmd = [shellcheck, '--source-path=SCRIPTDIR',
         '--enable=%s' % ','.join(extra_checks)]
  if output_format != 'default':
    cmd.extend(SHLINT_OUTPUT_FORMAT_MAP[output_format])
  cmd.append('-x')
  if gentoo_format:
    # ebuilds don't explicitly export variables or contain a shebang.
    cmd.append('--exclude=SC2148')
    # ebuilds always use bash.
    cmd.append('--shell=bash')
  cmd.append(path)

  lint_result = _LinterRunCommand(cmd, debug)

  # During testing, we don't want to fail the linter for shellcheck errors,
  # so override the return code.
  if lint_result.returncode != 0:
    bug_url = (
        'https://bugs.chromium.org/p/chromium/issues/entry?' +
        urllib.parse.urlencode({
            'template':
                'Defect report from Developer',
            'summary':
                'Bad shellcheck warnings for %s' % os.path.basename(path),
            'components':
                'Infra>Client>ChromeOS>Build,',
            'cc':
                'bmgordon@chromium.org,vapier@chromium.org',
            'comment':
                'Shellcheck output from file:\n%s\n\n<paste output here>\n\n'
                "What is wrong with shellcheck's findings?\n" % path,
        }))
    logging.warn('Shellcheck found problems. These will eventually become '
                 'errors.  If the shellcheck findings are not useful, '
                 'please file a bug at:\n%s', bug_url)
    lint_result.returncode = 0
  return lint_result


def _GentooShellLintFile(path, output_format, debug):
  """Run shell checks with Gentoo rules."""
  return _ShellLintFile(path, output_format, debug, gentoo_format=True)


def _BreakoutDataByLinter(map_to_return, path):
  """Maps a linter method to the content of the |path|."""
  # Detect by content of the file itself.
  try:
    with open(path) as fp:
      # We read 128 bytes because that's the Linux kernel's current limit.
      # Look for BINPRM_BUF_SIZE in fs/binfmt_script.c.
      data = fp.read(128)

      if not data.startswith('#!'):
        # If the file doesn't have a shebang, nothing to do.
        return

      m = SHEBANG_RE.match(data)
      if m:
        prog = m.group(1)
        if prog == '/usr/bin/env':
          prog = m.group(3)
        basename = os.path.basename(prog)
        if basename.startswith('python'):
          pylint_list = map_to_return.setdefault(_PylintFile, [])
          pylint_list.append(path)
        elif basename in ('sh', 'dash', 'bash'):
          shlint_list = map_to_return.setdefault(_ShellLintFile, [])
          shlint_list.append(path)
  except IOError as e:
    logging.debug('%s: reading initial data failed: %s', path, e)


# Map file extensions to a linter function.
_EXT_TO_LINTER_MAP = {
    # Note these are defined to keep in line with cpplint.py. Technically, we
    # could include additional ones, but cpplint.py would just filter them out.
    frozenset({'.cc', '.cpp', '.h'}): _CpplintFile,
    frozenset({'.json'}): _JsonLintFile,
    frozenset({'.py'}): _PylintFile,
    frozenset({'.go'}): _GolintFile,
    frozenset({'.sh'}): _ShellLintFile,
    frozenset({'.ebuild', '.eclass', '.bashrc'}): _GentooShellLintFile,
    frozenset({'.md'}): _MarkdownLintFile,
}


def _BreakoutFilesByLinter(files):
  """Maps a linter method to the list of files to lint."""
  map_to_return = {}
  for f in files:
    extension = os.path.splitext(f)[1]
    for extensions, linter in _EXT_TO_LINTER_MAP.items():
      if extension in extensions:
        todo = map_to_return.setdefault(linter, [])
        todo.append(f)
        break
    else:
      if os.path.isfile(f):
        _BreakoutDataByLinter(map_to_return, f)

  return map_to_return


def _FilterFiles(files):
  """Filter out ignored files.

  Note: This is currently just a special case for generated protobuf files. If
  there are more use cases, then a better configuration scheme should at least
  be incorporated. This can also be removed in favor of built in ignore
  functionality as we update our pylint versions.

  Pylint --ignore-patterns did not get introduced until pylint 1.6 and the
  --ignore functionality wasn't correctly applied to directories through
  asteroid 1.6, at least when given a file directly (as we do):
  http://pylint.pycqa.org/en/latest/whatsnew/changelog.html#what-s-new-in-pylint-1-6-0
  https://github.com/PyCQA/pylint/issues/1700

  TODO(saklein) Check the builtin ignore functionality as we upgrade pylint and
  remove this function if/when possible.
  """
  return [f for f in files if not f.endswith('_pb2.py')]


def _Dispatcher(errors, output_format, debug, linter, path):
  """Call |linter| on |path| and take care of coalescing exit codes/output."""
  result = linter(path, output_format, debug)
  if result.returncode:
    with errors.get_lock():
      errors.value += 1


@command.CommandDecorator('lint')
class LintCommand(command.CliCommand):
  """Run lint checks on the specified files."""

  EPILOG = """
Right now, only supports cpplint and pylint. We may also in the future
run other checks (e.g. pyflakes, etc.)
"""

  # The output formats supported by cros lint.
  OUTPUT_FORMATS = ('default', 'colorized', 'msvs', 'parseable')

  @classmethod
  def AddParser(cls, parser):
    super(LintCommand, cls).AddParser(parser)
    parser.add_argument('files', help='Files to lint', nargs='*')
    parser.add_argument('--output', default='default',
                        choices=LintCommand.OUTPUT_FORMATS,
                        help='Output format to pass to the linters. Supported '
                        'formats are: default (no option is passed to the '
                        'linter), colorized, msvs (Visual Studio) and '
                        'parseable.')

  def Run(self):
    files = self.options.files
    if not files:
      # Running with no arguments is allowed to make the repo upload hook
      # simple, but print a warning so that if someone runs this manually
      # they are aware that nothing was linted.
      logging.warning('No files provided to lint.  Doing nothing.')

    errors = multiprocessing.Value('i')
    linter_map = _BreakoutFilesByLinter(_FilterFiles(files))
    dispatcher = functools.partial(_Dispatcher, errors,
                                   self.options.output, self.options.debug)

    # Special case one file as it's common -- faster to avoid parallel startup.
    if sum(len(x) for x in linter_map.values()) == 1:
      linter, files = next(iter(linter_map.items()))
      dispatcher(linter, files[0])
    else:
      # Run the linter in parallel on the files.
      with parallel.BackgroundTaskRunner(dispatcher) as q:
        for linter, files in linter_map.items():
          for path in files:
            q.put([linter, path])

    if errors.value:
      logging.error('Found lint errors in %i files.', errors.value)
      sys.exit(1)